Treprostinil administration by inhalation

ABSTRACT

Treprostinil can be administered using a metered dose inhaler. Such administration provides a greater degree of autonomy to patients. Also disclosed are kits that include a metered dose inhaler containing a pharmaceutical formulation containing treprostinil.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of U.S. application Ser. No. 16/536,954, filed Aug. 9, 2019, which is a Continuation of U.S. application Ser. No. 15/011,999, filed Feb. 1, 2016, which is a Divisional of U.S. application Ser. No. 13/469,854, filed May 11, 2012, Divisional of U.S. application Ser. No. 12/591,200, filed Nov. 12, 2009, which is a Continuation of U.S. application Ser. No. 11/748,205, filed May 14, 2007, which claims priority to U.S. provisional application No. 60/800,016 filed May 15, 2006, which are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present application relates to methods and kits for therapeutic treatment and, more particularly, to therapeutic methods involving administering treprostinil using a metered dose inhaler and related kits.

BACKGROUND OF THE INVENTION

All blood is driven through the lungs via the pulmonary circulation in order, among other things, to replenish the oxygen which it dispenses in its passage around the rest of the body via the systemic circulation. The flow through both circulations is in normal circumstances equal, but the resistance offered to it in the pulmonary circulation is generally much less than that of the systemic circulation. When the resistance to pulmonary blood flow increases, the pressure in the circulation is greater for any particular flow. The above described condition is referred to as pulmonary hypertension (PH). Generally, pulmonary hypertension is defined through observations of pressures above the normal range pertaining in the majority of people residing at the same altitude and engaged in similar activities.

Pulmonary hypertension may occur due to various reasons and the different entities of pulmonary hypertension were classified based on clinical and pathological grounds in 5 categories according to the latest WHO convention, see e.g. Simonneau G., et al. J. Am. Coll. Cardiol. 2004; 43(12 Suppl S):5S-12S. Pulmonary hypertension can be a manifestation of an obvious or explicable increase in resistance, such as obstruction to blood flow by pulmonary emboli, malfunction of the heart's valves or muscle in handling blood after its passage through the lungs, diminution in pulmonary vessel caliber as a reflex response to alveolar hypoxia due to lung diseases or high altitude, or a mismatch of vascular capacity and essential blood flow, such as shunting of blood in congenital abnormalities or surgical removal of lung tissue. In addition, certain infectious diseases, such as HIV and liver diseases with portal hypertension may cause pulmonary hypertension. Autoimmune disorders, such as collagen vascular diseases, also often lead to pulmonary vascular narrowing and contribute to a significant number of pulmonary hypertension patients. The cases of pulmonary hypertension remain where the cause of the increased resistance is as yet inexplicable are defined as idiopathic (primary) pulmonary hypertension (iPAH) and are diagnosed by and after exclusion of the causes of secondary pulmonary hypertension and are in the majority of cases related to a genetic mutation in the bone morphogenetic protein receptor-2 gene. The cases of idiopathic pulmonary arterial hypertension tend to comprise a recognizable entity of about 40% of patients cared for in large specialized pulmonary hypertension centers. Approximately 65% of the most commonly afflicted are female and young adults, though it has occurred in children and patients over 50. Life expectancy from the time of diagnosis is short without specific treatment, about 3 to 5 years, though occasional reports of spontaneous remission and longer survival are to be expected given the nature of the diagnostic process. Generally, however, disease progress is inexorable via syncope and right heart failure and death is quite often sudden.

Pulmonary hypertension refers to a condition associated with an elevation of pulmonary arterial pressure (PAP) over normal levels. In humans, a typical mean PAP is approximately 12-15 mm Hg. Pulmonary hypertension, on the other hand, can be defined as mean PAP above 25 mmHg, assessed by right heart catheter measurement. Pulmonary arterial pressure may reach systemic pressure levels or even exceed these in severe forms of pulmonary hypertension. When the PAP markedly increases due to pulmonary venous congestion, i.e. in left heart failure or valve dysfunction, plasma can escape from the capillaries into the lung interstitium and alveoli. Fluid buildup in the lung (pulmonary edema) can result, with an associated decrease in lung function that can in some cases be fatal. Pulmonary edema, however, is not a feature of even severe pulmonary hypertension due to pulmonary vascular changes in all other entities of this disease.

Pulmonary hypertension may either be acute or chronic. Acute pulmonary hypertension is often a potentially reversible phenomenon generally attributable to constriction of the smooth muscle of the pulmonary blood vessels, which may be triggered by such conditions as hypoxia (as in high-altitude sickness), acidosis, inflammation, or pulmonary embolism. Chronic pulmonary hypertension is characterized by major structural changes in the pulmonary vasculature, which result in a decreased cross-sectional area of the pulmonary blood vessels. This may be caused by, for example, chronic hypoxia, thromboembolism, collagen vascular diseases, pulmonary hypercirculation due to left-to-right shunt, HIV infection, portal hypertension or a combination of genetic mutation and unknown causes as in idiopathic pulmonary arterial hypertension.

Pulmonary hypertension has been implicated in several life-threatening clinical conditions, such as adult respiratory distress syndrome (“ARDS”) and persistent pulmonary hypertension of the newborn (“PPHN”). Zapol et al., Acute Respiratory Failure, p. 241-273, Marcel Dekker, New York (1985); Peckham, J. Ped. 93:1005 (1978). PPHN, a disorder that primarily affects full-term infants, is characterized by elevated pulmonary vascular resistance, pulmonary arterial hypertension, and right-to-left shunting of blood through the patent ductus arteriosus and foramen ovale of the newborn's heart. Mortality rates range from 12-50%. Fox, Pediatrics 59:205 (1977); Dworetz, Pediatrics 84:1 (1989). Pulmonary hypertension may also ultimately result in a potentially fatal heart condition known as “cor pulmonale,” or pulmonary heart disease. Fishman, “Pulmonary Diseases and Disorders” 2^(nd) Ed., McGraw-Hill, New York (1988).

Currently, there is no treatment for pulmonary hypertension that can be administered using a compact inhalation device, such as a metered dose inhaler.

SUMMARY OF THE INVENTION

One embodiment is a method of delivering to a subject in need thereof a therapeutically effective amount of treprostinil, or treprostinil derivative or a pharmaceutically acceptable salt thereof comprising administering to the subject a therapeutically effective amount of the treprostinil or treprostinil derivative or a pharmaceutically acceptable salt thereof using a metered dose inhaler.

Another embodiment is a method for treating pulmonary hypertension comprising administering to a subject in need thereof treprostinil or its derivative, or a pharmaceutically acceptable salt thereof using a metered dose inhaler.

Yet another embodiment is a kit comprising a metered dose inhaler containing a pharmaceutical formulation comprising treprostinil or treprostinil derivative, or a pharmaceutically acceptable salt thereof.

And yet another embodiment is a kit for treating pulmonary hypertension in a subject, comprising (i) an effective amount of treprostinil or its derivative, or a pharmaceutically acceptable salt thereof; (ii) a metered dose inhaler; (iii) instructions for use in treating pulmonary hypertension.

Administration of treprostinil using a metered dose inhaler can provide patients, such as pulmonary hypertension patients, with a high degree of autonomy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 pulmonary and systemic changes in hemodynamics following the inhalation of placebo (open circles), 30 μg treprostinil (triangles), 45 μg treprostinil (squares) or 60 μg TREprostinil (black circles) applied by a Metered Dose Inhaler (MDI-TRE). A single short inhalation of treprostinil induced sustained reduction of PAP and PVR that outlasted the observation period of 120 minutes at doses of 45 and 60 μg MDI-TRE. Systemic arterial pressure and resistance were not significantly affected. PAP=mean pulmonary artery pressure; PVR=pulmonary vascular resistance; SAP=mean systemic arterial pressure; SVR=systemic vascular resistance. Data are given as mean value±standard error of the mean (SEM).

FIG. 2 presents hemodynamic changes induced by the inhalation of placebo (open circles), 30 μg treprostinil (triangles), 45 μg treprostinil (squares) or 60 μg treprostinil (black circles) applied by a metered dose inhaler. Treprostinil induced sustained elevation of cardiac output. Heart rate was rather unchanged as a sign for low spillover of MDI-TRE to the systemic circulation. Gas exchange was not negatively affected. CO=cardiac output; HR=heart rate; SaO2=arterial oxygen saturation; SvO2=central venous oxygen saturation. Data are given as mean value±SEM.

FIG. 3 shows areas under the curve for changes in pulmonary vascular resistance (PVR) calculated for an observation period of 120 minutes after inhalation treprostinil using a metered dose inhaler. PVR was markedly lowered by treprostinil inhalation. The increased pulmonary vasodilation over time with the two highest doses mainly relies on the more sustained effect over time. Data are shown as mean value±95% confidence intervals.

FIG. 4 demonstrates Ventilation-perfusion matching measured with the multiple inert gas elimination technique. Five patients (30 μg TRE, n=2; 45 μg TRE, n=1; 60 μg TRE, n=2) with pre-existing gas exchange problems were investigated for changes in ventilation-perfusion ratios. All patients had significant shunt flow at baseline. Shunt-flow and low V/Q areas were not significantly changed by nitric oxide (NO) inhalation or treprostinil inhalation using a metered dose inhaler (MDI-TRE). MDI-TRE applied at high treprostinil concentrations did not negatively affect ventilation-perfusion matching and gas-exchange. Data are given as mean value±95% confidence intervals.

FIG. 5 presents response of pulmonary vascular resistance (PVR) to inhaled treprostinil vs. iloprost—period effects. a) First inhalation with treprostinil (n=22) vs. first inhalation with iloprost (n=22); b) second inhalation with treprostinil (n=22) vs. second inhalation with iloprost (n=22). The PVR decrease with treprostinil was delayed and prolonged, compared to iloprost. Due to carryover effects from the first period, in the second period, the effects of both drugs appeared shortened. Data are shown as percent of baseline values (mean value±95% confidence interval).

FIG. 6 presents response of PVR and systemic arterial pressure (SAP) to inhalation of treprostinil vs. iloprost—dose effects. a) Inhalation of 7.5 μg iloprost (in 6 min) vs. 7.5 μg treprostinil (6 min) (n=14, in a randomized order). b) Inhalation of 7.5 μg iloprost (6 min) vs. 15 μg treprostinil (6 min) (n=14, in randomized order). c) Inhalation of 7.5 μg iloprost (6 min) vs. 15 μg treprostinil (3 min) (n=16, in randomized order). Data are shown as percent of baseline values (mean±95% confidence interval). Iloprost, filled circles; Treprostinil, open triangles.

FIG. 7 presents hemodynamic response to inhalation of treprostinil vs. iloprost. Data from n=44 patients, who inhaled both drugs in randomized order, shown as percent of baseline values (mean value±95% confidence interval). PVR, pulmonary vascular resistance; PAP, mean pulmonary arterial pressure; SAP, mean systemic arterial pressure; CO, cardiac output.

FIG. 8 presents pharmacodynamics after treprostinil inhalation vs. placebo. Placebo or treprostinil in doses of 30 μg, 60 μg or 90 μg were inhaled (means±95% confidence intervals). Maximal decrease of PVR was comparable for all doses. The duration of pulmonary vasodilation (PVR-decrease) appeared to be dose dependent. PVR, pulmonary vascular resistance; PAP, mean pulmonary arterial pressure; SAP, mean systemic arterial pressure; CO, cardiac output; SaO2, arterial oxygen saturation; SvO2, mixed venous oxygen saturation.

FIG. 9 presents Areas Between the placebo and the treprostinil Curves (ABC). ABCs were calculated for a 3-hour period after inhalation of TRE or placebo from the relative changes of hemodynamic parameters (means±95% confidence intervals). PVR, pulmonary vascular resistance; PAP, mean pulmonary arterial pressure; SAP, mean systemic arterial pressure; SVR, systemic vascular resistance.

FIG. 10 presents hemodynamic responses to the inhalation of 15 μg treprostinil. The inhalation time by increasing treprostinil concentration. A pulse of aerosol was generated every 6 seconds. TRE aerosol was inhaled in concentrations of 100 μg/ml (18 pulses; n=6), 200 μg/ml (9 pulses; n=6), 600 μg/ml (3 pulses; n=21), 1000 μg/ml (2 pulses; n=7) and 2000 μg/ml (1 pulse; n=8). Placebo data correspond to FIG. 8. Data are shown as means±95% confidence intervals. PVR, pulmonary vascular resistance; PAP, mean pulmonary arterial pressure; SAP, mean systemic arterial pressure; CO, cardiac output.

FIG. 11 presents areas between the placebo curve and the responses to 15 μg treprostinil applied at increasing concentrations to minimize inhalation time. Mean±SEM of relative changes of hemodynamic parameters (observation time 120 min). PAP, pulmonary arterial pressure, SAP, systemic arterial pressure, PVR, pulmonary vascular resistance, CO, cardiac output, SaO2, systemic arterial oxygen saturation, SvO2, pulmonary arterial oxygen saturation.

FIG. 12 presents pharmacokinetics of treprostinil after a single inhalation. Treprostinil plasma levels after inhalation of 30 μg, 60 μg, 90 μg or 120 μg treprostinil (6 min inhalation period; experiments correspond to those shown in FIGS. 8 and 9). Data with error bars represent mean values±SEM.

DETAILED DESCRIPTION OF THE INVENTION

Unless otherwise specified, the term “a” or “an” used herein shall mean “one or more.”

The present application incorporates herein by reference in its entirety Voswinckel R, et al. J. Am. Coll. Cardiol. 2006; 48:1672-1681.

The inventors discovered that a therapeutically effective dose of treprostinil can be administered in a few single inhalations using a compact inhalation device, such as a metered dose inhaler. Furthermore, the inventors discovered that such administering does not cause significant side effects, especially no significant side effects related to systemic blood pressure and circulation as well as no gas exchange deteriorations or disruptions.

Accordingly, one embodiment of the invention is a method of delivering to a subject in need thereof, such as a human being, a therapeutically effective amount of treprostinil comprising administering to the subject a formulation comprising a therapeutically effective amount of treprostinil, its derivative or a pharmaceutically acceptable salt thereof using a metered dose inhaler. Treprostinil can be administered via a metered dose inhaler to a subject affected with a condition or disease, which can be treated by treprostinil, such as asthma, pulmonary hypertension, peripheral vascular disease or pulmonary fibrosis.

Another embodiment of the invention is a method for treating pulmonary hypertension, comprising administering to a subject in need thereof, such as a human being, treprostinil or its derivative, or a pharmaceutically acceptable salt using a metered dose inhaler.

Treprostinil, or 9-deoxy-2′,9-alpha-methano-3-oxa-4,5,6-trinor-3,7-(1′3′-interphenylene)-13,14-dihydro-prostaglandin F1, is a prostacyclin analogue, first described in U.S. Pat. No. 4,306,075. U.S. Pat. No. 5,153,222 describes use of treprostinil for treatment of pulmonary hypertension. Treprostinil is approved for the intravenous as well as subcutaneous route, the latter avoiding septic events associated with continuous intravenous catheters. U.S. Pat. Nos. 6,521,212 and 6,756,033 describe administration of treprostinil by inhalation for treatment of pulmonary hypertension, peripheral vascular disease and other diseases and conditions. U.S. Pat. No. 6,803,386 discloses administration of treprostinil for treating cancer such as lung, liver, brain, pancreatic, kidney, prostate, breast, colon and head-neck cancer. US patent application publication No. 2005/0165111 discloses treprostinil treatment of ischemic lesions. U.S. Pat. No. 7,199,157 discloses that treprostinil treatment improves kidney functions. US patent application publication No. 2005/0282903 discloses treprostinil treatment of neuropathic foot ulcers. U.S. provisional application No. 60/900,320 filed Feb. 9, 2007, discloses treprostinil treatment of pulmonary fibrosis.

The term “acid derivative” is used herein to describe C1-4 alkyl esters and amides, including amides wherein the nitrogen is optionally substituted by one or two C1-4 alkyl groups.

The present invention also encompasses methods of using Treprostinil or its derivatives, or pharmaceutically acceptable salts thereof. In one embodiment, a method uses Treprostinil sodium, currently marketed under the trade name of REMODULIN®. The FDA has approved Treprostinil sodium for the treatment of pulmonary arterial hypertension by injection of dose concentrations of 1.0 mg/mL, 2.5 mg/mL, 5.0 mg/mL and 10.0 mg/mL. The chemical structure formula for Treprostinil sodium is:

Treprostinil sodium is sometimes designated by the chemical names: (a) [(1R,2R,3aS,9aS)-2,3,3a,4,9,9a-hexahydro-2-hydroxy-1-[(3S)-3-hydroxyoctyl]-1H-benz[f]inden-5-yl]oxy]acetic acid; or (b) 9-deoxy-2′,9-α-methano-3-oxa-4,5,6-trinor-3,7-(1′,3′-interphenylene)-13,14-dihydro-prostaglandin F₁. Treprostinil sodium is also known as: UT-15; LRX-15; 15AU81; UNIPROST™; BW A15AU; and U-62,840. The molecular weight of Treprostinil sodium is 390.52, and its empirical formula is C₂₃H₃₄O₅.

In certain embodiments, treprostinil can be administered in combination with one or more additional active agents. In some embodiments, such one or more additional active agents can be also administered together with treprostinil using a metered dose inhaler. Yet in some embodiments, such one or more additional active agents can be administered separately from treprostinil. Particular additional active agents that can be administered in combination with treprostinil may depend on a particular disease or condition for treatment or prevention of which treprostinil is administered. In some cases, the additional active agent can be a cardiovascular agent such as a calcium channel blocker, a phosphodiesterase inhibitor, an endothelial antagonist, or an antiplatelet agent.

The present invention extends to methods of using physiologically acceptable salts of Treprostinil, as well as non-physiologically acceptable salts of Treprostinil that may be used in the preparation of the pharmacologically active compounds of the invention.

The term “pharmaceutically acceptable salt” refers to a salt of Treprostinil with an inorganic base, organic base, inorganic acid, organic acid, or basic or acidic amino acid. Salts of inorganic bases can be, for example, salts of alkali metals such as sodium or potassium; alkaline earth metals such as calcium and magnesium or aluminum; and ammonia. Salts of organic bases can be, for example, salts trimethylamine, triethylamine, pyridine, picoline, ethanolamine, diethanolamine, and triethanolamine. Salts of inorganic acids can be, for example, salts of hydrochloric acid, hydroboric acid, nitric acid, sulfuric acid, and phosphoric acid. Salts of organic acids can be, for example, salts of formic acid, acetic acid, trifluoroacetic acid, fumaric acid, oxalic acid, lactic acid, tartaric acid, maleic acid, citric acid, succinic acid, malic acid, methanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid. Salts of basic amino acids can be, for example, salts of arginine, lysine and ornithine. Salts of acidic amino acids can include, for example, salts of aspartic acid and glutamic acid. Quaternary ammonium salts can be formed, for example, by reaction with lower alkyl halides, such as methyl, ethyl, propyl, and butyl chlorides, bromides, and iodides, with dialkyl sulphates, with long chain halides, such as decyl, lauryl, myristyl, and stearyl chlorides, bromides, and iodides, and with aralkyl halides, such as benzyl and phenethyl bromides.

Preferred pharmaceutically acceptable salts are disclosed, for example, in US patent application publication No. 20050085540.

Treprostinil can be administered by inhalation, which in the present context refers to the delivery of the active ingredient or a combination of active ingredients through a respiratory passage, wherein the subject in need of the active ingredient(s) through the subject's airways, such as the subject's nose or mouth.

A metered dose inhaler in the present context means a device capable of delivering a metered or bolus dose of respiratory drug, such as treprostinil, to the lungs. One example of the inhalation device can be a pressurized metered dose inhaler, a device which produces the aerosol clouds for inhalation from solutions and/or suspensions of respiratory drugs in chlorofluorocarbon (CFC) and/or hydrofluoroalkane (HFA) solutions.

The inhalation device can be also a dry powder inhaler. In such case, the respiratory drug is inhaled in solid formulation, usually in the form of a powder with particle size less than 10 micrometers in diameter or less than 5 micrometers in diameter.

The metered dose inhaler can be a soft mist inhaler (SMI), in which the aerosol cloud containing a respiratory drug can be generated by passing a solution containing the respiratory drug through a nozzle or series of nozzles. The aerosol generation can be achieved in SMI, for example, by mechanical, electromechanical or thermomechanical process. Examples of soft mist inhalers include the Respimat® Inhaler (Boeringer Ingelheim GmbH), the AERx® Inhaler (Aradigm Corp.), the Mystic™ Inhaler (Ventaira Pharmaceuticals, Inc) and the Aira™ Inhaler (Chrysalis Technologies Incorporated). For a review of soft mist inhaler technology, see e.g. M. Hindle, The Drug Delivery Companies Report, Autumn/Winter 2004, pp. 31-34. The aerosol for SMI can be generated from a solution of the respiratory drug further containing pharmaceutically acceptable excipients. In the present case, the respiratory drug is treprostinil, its derivative or a pharmaceutically acceptable salt thereof, which can be formulated in SMI is as a solution. The solution can be, for example, a solution of treprostinil in water, ethanol or a mixture thereof. Preferably, the diameter of the treprostinil-containing aerosol particles is less than about 10 microns, or less than about 5 microns, or less than about 4 microns.

Treprostinil concentration in an aerosolable formulation, such as a solution, used in a metered dose inhaler can range from about 500 μg/ml to about 2500 μg/ml, or from about 800 μg/ml to about 2200 μg/ml, or from about 1000 μg/ml to about 2000 μg/ml.

The dose of treprostinil that can be administered using a metered dose inhaler in a single event can be from about 15 μg to about 100 μg or from about 15 μg to about 90 μg or from about 30 μg to about 90 μg or from about 30 μg to about 60 μg.

Administering of treprostinil in a single event can be carried out in a limited number of breaths by a patient. For example, treprostinil can be administered in 20 breaths or less, or in 10 breaths or less, or than 5 breaths or less. Preferably, treprostinil is administered in 3, 2 or 1 breaths.

The total time of a single administering event can be less than 5 minutes, or less than 1 minute, or less than 30 seconds.

Treprostinil can be administered a single time per day or several times per day.

In some embodiments, the method of treatment of pulmonary hypertension can further comprise administering at least one supplementary agent selected from the group consisting of sildenafil, tadalafil, calcium channel blockers (diltiazem, amlodipine, nifedipine), bosentan, sitaxsentan, ambrisentan, and pharmaceutically acceptable salts thereof. In some embodiments, the supplementary agents can be included in the treprostinil formulation and, thus, can be administered simultaneously with treprostinil using a metered dose inhaler. In some embodiments, the supplementary agents can be administered separately from treprostinil. In some embodiments, the application of intravenous prostacyclin (flolan), intravenous iloprost or intravenous or subcutaneous treprostinil can be administered in addition to treprostinil administered via inhalation using a metered dose inhaler.

The present invention also provides a kit that includes a metered dose inhaler containing a pharmaceutical formulation comprising treprostinil or its derivative, or a pharmaceutically acceptable salt thereof. Such a kit can further include instructions on how to use the metered dose inhaler for inhaling treprostinil. Such instructions can include, for example, information on how to coordinate patient's breathing, and actuation of the inhaler. The kit can be used by a subject, such as human being, affected with a disease or condition that can be treated by treprostinil, such as asthma, pulmonary hypertension, peripheral vascular disease or pulmonary fibrosis.

In some cases, the kit is a kit for treating pulmonary hypertension, that includes (i) a metered dose inhaler containing a pharmaceutical formulation comprising treprostinil or its derivative, or a pharmaceutically acceptable salt thereof; and (ii) instructions for use of the metered dose inhaler containing treprostinil in treating pulmonary hypertension.

As used herein, the phrase “instructions for use” shall mean any FDA-mandated labeling, instructions, or package inserts that relate to the administration of Treprostinil or its derivatives, or pharmaceutically acceptable salts thereof, for treatment of pulmonary hypertension by inhalation. For example, instructions for use may include, but are not limited to, indications for pulmonary hypertension, identification of specific symptoms associated with pulmonary hypertension, that can be ameliorated by Treprostinil, recommended dosage amounts for subjects suffering from pulmonary hypertension and instructions on coordination of individual's breathing and actuation of the metered dose inhaler.

The present invention can be illustrated in more detail by the following example, however, it should be understood that the present invention is not limited thereto. 

What is claimed is:
 1. A method of treating pulmonary hypertension comprising: providing an inhalation device for treating pulmonary hypertension in a human suffering from pulmonary hypertension comprising a formulation of treprostinil or a pharmaceutically acceptable salt thereof and an inhalation device configured to administer a therapeutically effective single event dose of the formulation comprising treprostinil or a pharmaceutically acceptable salt thereof, wherein the therapeutically effective single event dose comprises from 15 micrograms to 90 micrograms of treprostinil or a pharmaceutically acceptable salt thereof delivered in 1 to 3 breaths, wherein the inhaler is configured to administer the entire therapeutically effective single event dose in less than 5 minutes with at least 5 micrograms of treprostinil or a pharmaceutically acceptable salt thereof being inhaled per breath through coordinated actuation of the inhaler with each breath, and administering to a human suffering from pulmonary hypertension with the inhalation device the therapeutically effective single event dose comprising from 15 micrograms to 90 micrograms of treprostinil or a pharmaceutically acceptable salt thereof in 1 to 3 breaths, wherein the human administers the entire therapeutically effective single event dose with the inhalation device in less than 5 minutes by inhaling at least 5 micrograms of treprostinil or a pharmaceutically acceptable salt thereof per breath by coordinating one actuation of the inhaler for each separate breath, and wherein administration of an additional therapeutically single event dose in the same manner occurs at least 3 hours later.
 2. The method of claim 1, further comprising administering at least 3 hours later an additional therapeutically effective single event dose comprising from 15 micrograms to 90 micrograms of treprostinil or a pharmaceutically acceptable salt thereof in 1 to 3 breaths, wherein the human administers the entire therapeutically effective single event dose with the inhalation device in less than 5 minutes by inhaling at least 5 micrograms of treprostinil or a pharmaceutically acceptable salt thereof per breath by coordinating one actuation of the inhaler for each separate breath.
 3. The method of claim 1, wherein the human administers the therapeutically effective single event dose several times per day.
 4. The method of claim 1, wherein the inhalation device is a nebulizer or a dry powder inhaler.
 5. The method of claim 4, wherein the formulation comprises particles less than 5 micrometers in diameter.
 6. The method of claim 1, wherein the formulation contains no metacresol.
 7. The method of claim 1, wherein the human inhales each therapeutically effective single event dose in less than about 1 minute.
 8. The method of claim 1, wherein the inhalation device is configured to administer at least 15 micrograms of treprostinil or its pharmaceutically effective salt per breath and the human inhales at least 15 micrograms of treprostinil or a pharmaceutically acceptable salt thereof per breath by coordinating one actuation of the inhaler for each separate breath.
 9. The method of claim 1, wherein the therapeutically effective single event dose provides a maximal treprostinil plasma concentration in the human of at least 0.65±0.28 ng/ml.
 10. The method of claim 1, wherein the therapeutically effective single event dose provides a peak plasma concentration of treprostinil in the human at about 10-15 minutes after inhalation. 